Why does Galaxy Tab a8 landscape layout disable button on the bottom of the page

I have Desktop version 21.4. Using an iPad this works as expected. However, using a Galaxy Tab A8 the footer buttons on my page (navigation and resources) only function if the browser window header is also visible. The browser header has a tenancy to hide. So to get the buttons to function I have to do some weird two finger swipe to shrink the page enough for the browser header to show, and at the same time have the page footer show. I've set the page size height really small (500 pixels) and it seems to have no effect. The page seems to continue to be the same height. I've got 'Auto page height' off. Anybody know what could be causing this? Thanks